Conclusion
Evaporation-driven WEG devices have gained significant attention since
water is highly available and can easily evaporate. Several studies
utilizing inorganic nanomaterials tend to overshadow the utilization of
easily accessible organic materials. This study presents an innovative
electricity generation method that employs the nutshell (NS) structures
by leveraging the process of streaming potential and water evaporations.
This revolutionary bio-based technology is presented for the first time
and utilizes inherent hierarchical porous structures of NSs for
efficient ion transfer, enabling the WEG device to function sustainably
with minimum water intake. Amongst the four NSs investigated, walnut
shell (WS) exhibits superior performance due to its uniform pore
distributions, surface charge, and efficient water uptake and release
capabilities. Other NSs are also a promising source of WEG that need
further attention. A consistent electric output over 550 mV for a
duration of one week, demonstrates the long-term stability of the
WS-WEG. Moreover, this WS-WEG functional device’s incredible power
density (5.96 µW·cm−2) indicates its enormous
potential for practical use. A notable enhancement of the voltage and
current density is observed by utilizing nanoengineering techniques that
enhance the number of nanopores. Furthermore, placing the
nano-engineered WS-H+ into an alkaline reservoir shows
a significant rise in voltage to 1.21 V and a maximum current density of
347.2 μA/cm2. This enhancement could be attributed to
the combined synergetic impacts of physical and chemical mechanisms. By
connecting two units in series and two units in parallel, this
WS-H+ can power a calculator without the aid of any
rectifiers, indicating the potentiality of this WEG device as a
sustainable power source for compact electronics. In summary, this work
not only develops the comprehension of nutshell-based WEG but also
offers a feasible, low-cost, sustainable energy source utilizing
agro-industrial waste to power electronic devices.